Head-to-head comparison across 6benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
Claude Opus 4.5
77
Gemini 3.5 Flash
88
Verified leaderboard positions: Claude Opus 4.5 #11 · Gemini 3.5 Flash #7
Pick Gemini 3.5 Flash if you want the stronger benchmark profile. Claude Opus 4.5 only becomes the better choice if coding is the priority or you would rather avoid the extra latency and token burn of a reasoning model.
Agentic
+14.7 difference
Coding
+11.4 difference
Reasoning
+10.3 difference
Knowledge
+8.2 difference
Multimodal
+13.8 difference
Inst. Following
+3.1 difference
Claude Opus 4.5
Gemini 3.5 Flash
$5 / $25
$1.5 / $9
46 t/s
284.2 t/s
1.01s
18.55s
200K
1M
Pick Gemini 3.5 Flash if you want the stronger benchmark profile. Claude Opus 4.5 only becomes the better choice if coding is the priority or you would rather avoid the extra latency and token burn of a reasoning model.
Gemini 3.5 Flash is clearly ahead on the provisional aggregate, 88 to 77. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
Gemini 3.5 Flash's sharpest advantage is in agentic, where it averages 77.2 against 62.5. The single biggest benchmark swing on the page is IFBench, 58% to 76.3%. Claude Opus 4.5 does hit back in coding, so the answer changes if that is the part of the workload you care about most.
Claude Opus 4.5 is also the more expensive model on tokens at $5.00 input / $25.00 output per 1M tokens, versus $1.50 input / $9.00 output per 1M tokens for Gemini 3.5 Flash. That is roughly 2.8x on output cost alone. Gemini 3.5 Flash is the reasoning model in the pair, while Claude Opus 4.5 is not. That usually helps on harder chain-of-thought-heavy tests, but it can also mean more latency and more token spend in real use. Gemini 3.5 Flash gives you the larger context window at 1M, compared with 200K for Claude Opus 4.5.
Gemini 3.5 Flash is ahead on BenchLM's provisional leaderboard, 88 to 77. The biggest single separator in this matchup is IFBench, where the scores are 58% and 76.3%.
Claude Opus 4.5 has the edge for knowledge tasks in this comparison, averaging 66.2 versus 58. Inside this category, HLE is the benchmark that creates the most daylight between them.
Claude Opus 4.5 has the edge for coding in this comparison, averaging 65.9 versus 54.5. Inside this category, SWE-bench Pro is the benchmark that creates the most daylight between them.
Gemini 3.5 Flash has the edge for reasoning in this comparison, averaging 74.7 versus 64.4. Claude Opus 4.5 stays close enough that the answer can still flip depending on your workload.
Gemini 3.5 Flash has the edge for agentic tasks in this comparison, averaging 77.2 versus 62.5. Inside this category, MCP Atlas is the benchmark that creates the most daylight between them.
Gemini 3.5 Flash has the edge for multimodal and grounded tasks in this comparison, averaging 83.8 versus 70. Inside this category, CharXiv is the benchmark that creates the most daylight between them.
Claude Opus 4.5 has the edge for instruction following in this comparison, averaging 79.4 versus 76.3. Inside this category, IFBench is the benchmark that creates the most daylight between them.
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